ISDN is a great way for telecommuters and remote offices to establish high-speed RAS connections (i.e., for situations in which a 33.6 kilobits per second (Kbps) analog modem isn't fast enough). With ISDN, your system can accommodate analog modem calls transmitted from remote locations over the same phone circuit at speeds as fast as 56Kbps.
Two problems arise when you implement an ISDN solution: You must install an ISDN line and you must find the right ISDN interface. I can't offer advice on overcoming the first obstacle. But if you're a regular Windows NT Magazine reader, you might recall my battle with US West to install an ISDN line in my small office/home office (SOHO) lab (see John Enck, "Lab Guys," February, March, April, and May 1998). From that experience, I learned that some geographic areas have better ISDN service than Colorado has.
To find the right ISDN interface, examine Netaccess' server cards. Netaccess manufactures a full line of ISDN adapters, including two adapters for the Basic Rate Interface (BRI) market: IRAS-8 and IRAS-8A. These BRI adapters can handle as many as four BRI links (i.e., eight data channels). The IRAS-8 doesn't handle analog modem calls; it handles only digital calls (i.e., 64Kbps per channel). The IRAS-8A answers digital and analog modem calls at speeds as fast as 56Kbps. The IRAS-8A I tested supported only the K56Flex standard for 56Kbps operation. Currently, the IRAS-8A supports the new V.90 standard and the K56Flex standard for 56Kbps operation.
Basic Rate Interface or Primary Rate Interface
BRI and Primary Rate Interface (PRI) are the two types of ISDN links. The BRI line supports 2 data channels, and the PRI line supports 23 data channels. You can use each data channel for a 64Kbps digital connection. With the right equipment, you can also use each data channel or analog connection at speeds as fast as 56Kbps. Thus, one ISDN BRI link accommodates two 56Kbps analog connections, one 64Kbps digital connection and one 56Kbps analog connection, or two 64Kbps digital connections (which you can also combine into one 128Kbps connection).
Whether you install a PRI or one or more BRIs at a central location depends on cost and the number of concurrent RAS connections you need to accommodate. Pricing for PRIs and BRIs varies, but PRIs are typically more expensive than BRIs. For example, if you need to accommodate eight connections, installing four BRIs (eight data channels) might be more economical than installing one PRI.
Finding NT-compatible interfaces that handle BRI links is difficult: ISDN adapters for the NT market typically require PRI links. This forces NT aficionados who want BRI connections to implement ISDN modems or standalone routers. ISDN modems and routers work fine; however, hardcore NT administrators consider integrated BRI adapters ideal.
Deploying the IRAS-8A
Over the past several months, I've had the opportunity to deploy the IRAS-8A in the Windows NT Magazine Lab and use it daily. I installed the IRAS-8A in our Backup Domain Controller (BDC) and configured it for Remote Access Service (RAS). The hardware installation was painless because the IRAS-8A is a PCI adapter with no jumpers or DIP switches. You just open the computer, plug the adapter card into an empty PCI slot, and close the computer.
Installing the IRAS-8A drivers and related software was not as straightforward. However, as long as you read and follow the instructions in the documentation, your installation will go smoothly.
To install the software, you must first install the IRAS-8A driver. You invoke the driver-installation process when you run the Setup program on the 1.44MB hard disk that ships with the adapter. The Setup program also installs a Line Status tool, a Control Panel menu, and some supplemental online documentation.
After you install the driver, the Setup program opens the online documentation. This documentation includes steps to walk you through the rest of the IRAS-8A installation process and open the Control Panel menu. If you accidentally close the applet before completing the next step (as I did), you can go into Control Panel, open the Netaccess applet, and resume the installation process.
The Control Panel menu contains two configuration tabs: Adapters and Ports. When you select the Adapters tab, you can define the number and types of Netaccess ISDN adapters on your system. I configured one IRAS-8A adapter. To add the adapter, I clicked Add in the Adapters tab and selected the IRAS-8A entry from the list of available adapters. I clicked OK to confirm my selection, and the IRAS-8A appeared in the Adapters tab. When you select the Properties tab, you can configure the properties for each adapter. Screen 1, page 109, shows the Netaccess BRI Line Properties dialog box. You can configure the properties for each Netaccess line; each line corresponds to a separate BRI link. The properties consist of the type of switch your phone company uses, the type of ISDN connection you have, and the directory numbers and Service Profile Identifiers (SPIDs) for the BRI link on the ISDN connection.
You need to define the properties only for lines you use. For example, I installed an IRAS-8A adapter with four BRI links. Because I had only one BRI interface in the Lab, I configured only one of the four lines.
The ISDN information you enter isn't validated online: The IRAS-8A doesn't make a test connection to the phone company to confirm the information. You can perform that test later using the Line Status tool. Screen 2 shows the window you access this tool from. I had mixed feelings about the lack of online validation. Having some type of confirmation when configuring the ports is helpful, but the line status test isn't necessarily a good indicator of a working BRI link. Line status tests only confirm that the information you enter (e.g., switch type, interface type, SPID) matches what the phone company configures.
Wait! There's More!
When you configure the BRI links on the Adapters tab, the Netaccess applet automatically adds logical ports for each link. You can view these ports when you select the Ports tab. These ports become modem connections that you can use for RAS. I don't recommend altering properties for each port (the default values are appropriate for a RAS environment). My advice is to make sure the ports are present, then close the Control Panel menu.
After you define your adapter and BRI links and have several ports, you must add modem definitions so that RAS can access your ISDN connections. This process is simple: You invoke the Install New Modem wizard through the Modem applet in Control Panel. You tell the wizard to scan the IRAS-8A setup disk for the modem definition file. Then you associate the Netaccess modem definition with the logical ports the setup process generated. As part of the modem-installation process, the wizard gives you a list of available ports. You select the ports that correspond to your BRI links. After you make your selection, you complete the modem installation and begin installing or configuring RAS.
You install or configure RAS to work with the IRAS-8A in the same way you install or configure RAS to work with any off-the-shelf modem. If you want to provide support for 128Kbps BRI connections, you must enable the Multilink Point-to-Point Protocol (MPPP) during the RAS configuration dialog. If you don't have MPPP, you won't have 128Kbps connections. You'll have to reboot after you configure RAS.
I didn't test the IRAS-8A's RAS Access Manager. This administration tool lets you manage RAS users. You can monitor and report on user connection times, enable or disable concurrent single-user access, or set restrictions on the time users can spend using RAS. This tool seems to be targeted toward Internet Service Providers (ISPs) who don't like the native NT/RAS user-management tools.
The Ideal Connection
Installing the software isn't as simple as installing the hardware. However, after you complete the installation process, the IRAS-8A works very well. I tested the IRAS-8A using a variety of routers, ISDN modems, and K56Flex modems. In all cases, the IRAS-8A fielded my calls easily. Now that I have the IRAS-8A up and running, I can't think of anything that I don't like about it. The IRAS-8A is the ideal BRI connection that I've spent years searching for, and I'm glad I found it.
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